TM, difficult child 1 has the same problems any time he gets a cold. Like SRL, we break out the heavy artillery when happens (the "yellow" Advair, and even the "red" if he gets really bad). Fortunately, he's been fairly healthy this year. Maybe my hounding about hand washing is finally paying off!
Eekysign, I had asthma as a kid, and now I might have one wheezing episode per year. I think many people's immune systems change as they age and they are able to tolerate some allergic triggers as they get older. Also, our airways get larger as we grow into adulthood. It's probably a combination of factors. Then there are people like my brother who still cannot be in a house with a cat without having breathing problems -- and he's nearly 40.